Method of making metal alkyl compounds



May 1931.. E. c. BRITTON 1,805,756

METHOD OF MAKING METAL ALKYL COMPOUNDS Filed Nov. 16, 1926 2 Sheets-:Sheet 1 j/j 'gl.

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fagar C 52727012 May 19, 1931.

E. C. BRITTON METHOD OF MAKING METAL ALKYL COMPOUNDS MAGNESIUM LOW Bowma- SOLVENT (1TH an) Low BOILING SOLVENT (ETHEK) HYDROCH LORIL k A c :13

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(TOLUENE) LEAD SALT" ICE WATE-R.

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SQL VENT LAYER- HIGH BOILING SOLVEHT 1 LEAD (ToLuaNa) Te-rizA ALK'YL 6 INVENTOR.

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ATTORNEYS Patented my 19,1931

UNITED STATES PATENT OFFICE EDGAR C. BBIT'IOIKOF MIDLAND, MICHIGAN, ASSIGNOB To THE DOW GHEMIOAL M- PANY, OF MIDLAND,

MICHIGAN, A CORPORATION OF MICHIGAN METHOD OF MAKING METAL ALKYL COMPOUNDS Application filed November 16, 1926. Serial No. 148,714.

The present invention relates to methods for preparing metal alkyl compounds, more es ecially lead alkyl compounds, e. g. tetrat llead.

& Truskier, Ber. 37 1127 (1904) who reacted creases the magnesium, ethyl iodide and lead chloride in ether solution to form lead tetra/ethyl. The latter, however, decomposed on distillation producing. metallic lea and in order to prevent such decomposition, the tri-ethyl lead chloride was pre ared. Gruttner & Krause, Ber. 49, 1415 F1916), subsequently reported the preparat'on of lead tetraethyl as a distilled product by this reaction, but they were able to obtain only '85 grams of pure lead tetraethyl from 300 grams of ethyl magnesium bromide and 300 grams of lead chloride; a yield of only 38 per cent. on the lead chloride used.

I have discovered that, in any method for making organic compounds by the Grignard reaction, the action of heat on the addition product of any compound which adds to the organo-magnesium haloid complex inyield of the desired end product. That is, while the first stage of reaction can be conducted at lower temperatures, the temperature should be higher for the last stage. Where a low-boiling solvent, such for instance as ether, is used initially, this action of heat is best accomplished by adding a higher-boiling solvent as for example toluene, xylene, etc., to the reaction mixture and then distilling off the ether or low-boiling solvent, whereby the temperaturemay be elevated to any point determined. as the best for the reaction in hand. The foregoing discovery is of applicability not merely to the making of lead tetraethyl but other like organic compounds by the Grignard reaction.

This application is a continuation in part of my application Serial No. 389 filed J anne rly 3, 1924.

o the accomplishment of the foregoing and related ends, the invention, then, con-- sists of the steps hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the. following description setting forth in detail one approved method of carrying out the invention, such disclosed mode, however, constituting but one of the various ways in which the prin-- ciple ofthe invention may be used.

In said annexed drawings:-

Figure 1 is a diagrammatic, representation of-a special apparatusfor carrying out such improved method or process. Fig. 2 is a flow sheet illustrating the sequence of steps and movement of materials in the process as applied to the manufacture of a tetra-alkyl lead compound.

The apparatus thus shown may for convenience be first described. Such apparatus will be seen to consist of a reactor 1 on the order of a still that is provided with a steam coil 2 and a suitable externally driven stirrer 3. An opening (not shown) which may be properly sealed will also be provided for the convenient introduction of certain of the ingredients, as wellas a valve controlled outlet opening 4. at the bottom of the reactor. Connected with the latter by means of a duct 5 is a condenser coil 6 located in a cooling chamber 7, the lower end of such coil being connected with an absorber 8 from which a duct 9 leads back to the reactor. Said absorber, like the condenser, is located in a cooling chamber whereby the temperature of the returning condensate may be controlled, and connected with said absorber, preferably near its lower end, is a valve controlled duct 11 through which additional ingredients may be supplied to the condensate at this stage. For the purpose of withdrawing the condensate from the system, instead of returnin the same through duct 9 to reactor 1, a va ve controlled outlet 12 is provided at the lower end of the absorber. A vent 13 is also shown as leading from'the extension of the condenser coil 6 which connects the latter from 20 to minutes,

with the absorber.

The rocedure as applied for instance for preparing lead tetraethyl by the present improvedmethod and using the apparatus just described may be illustrated by the followingexample :1 pound of magnesium shavings is placed in the still or reactor 1 along with any usual or preferred solvent, as for example 5 pounds of ether, and, a crystal of iodine. To this, cooled and stirred as much as possible, is then added an ethyl halide, as for instance pound of ethyl bromide. The reaction of the latter and magnesium will proceed at once and generally cause the ether to boil. After this initial reaction is over, a mixture of ethyl halide and solvent, e. g. 3% pounds of ethyl bromide and 4 pounds of other is added gradually over a period of such additional amount f ethyl bromide completing the formation of the theoretical amount of ethyl magnesium bromide which constitutes the specific organo-magnesium haloid complex involved. The temperature during this stage should be approximately degrees C. or in any case below 50 degrees C. An organic solvent capable of providing a higher temperature, for instance 10 pounds of toluene, is added to the reaction mixture and then a salt of lead, e. g. 5 pounds of dry, powdered, technical chloride, the addition of the latter being spread over approximately 15 minutes and the temperature remaining at that last given. Next, the reaction mixture is refluxed at a temperature of from 67 to 70 degrees C. for 20 minutes, following which the ether, if such be used, is distilled off by raising the temperature in the reactor 1 to from 90 to 95 degrees C. and the mass refiuxed at this temperature for approximately three hours.

The reactions occurring during the procedure just describ-edimay be represented by the following equations e reaction product resulting from the foregoing steps consists ofa grayish black spongy mass which after cooling to 50 degrees C. is treated with ice and stirred, whereu on the whole becomes liquid and is drawn 0% into a suitable container. After acidifying to Congo red reaction, approximately 1 pounds of 30 per cent. hydrochloric acid,

Cl, being required, the mass is filtered and the filtrate put in a separator and allowed to settle thoroughly. After complete separation the upper toluene layer is removed and subjected to fractional distillation under vacuum. The remaining ether passes over first at low temperature, the toluene at 40 degrees C. and the lead tetraethyl at approximately 100 degrees 6., under a 28% inch vac- I uum.

As indicated, regardless of an solvents and whether or not pressure be used the matter of especial advantage which Iwish to make clearis the desirability of the application of considerable heat to the magnesium haloid addition complex reaction product of the desired metal, as itis thereby that the yield-increase of the desired end product is obtained.

As a general rule, the shorter the time of forming the magnesium compounds, the better yield one can obtain. While as at present advised ethyl bromide works better than ethyl chloride in the formation of the organomagnesium complex, this may be due to the presence of some impurity in such chloride which is detrimental to a Grignard reaction.

In using ethyl chloride as the organ halide, such chloride may be added as a liquid in solution with ether, or since it has a boiling point of 13 degrees 0., it may be introduced as a gas through pipe 11 into the return condensate,

or pressure can be used with either halide if preferred.

By initiating the Grignard reaction with ethyl bromide as the organic halide and then finishing with ethyl chloride, a much more rapid formation of Grignard compound can be realized than alone. If ethyl bromide is used instead of ethyl chloride, it may be entered into the reaction by being introduced into the returning distillate, or since it is a liquid at normal temperatures, it may be introduced directly into the reaction chamber.

Other modes of applying the principle of my invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of'such stated step or steps be employed.

I therefore particularly point out and distinctly claim as my invention 1. In a method of making a metal alkyl compound, the step which consists in heating the initial reaction product of an alkyl magnesium'halide and a halide of the metal at a temperature above 50 C.

2. In a method of making a metal alkyl compound, the steps which consist in reacting between an alkyl-magnesium halide and a halide of the metal at a temperature not much exceeding room temperature and subjecting the product so formed to a materially higher temperature.

3. In a method of making a metal alkyl compound, the steps which consist in reacting between an alkyl-magnesium halide. and a halide of the metal at a temperature below 50 (1, and heating the product so formed to a temperature materially above 50 C.

by using ethyl chloride com ound, the step which consists in reacting etween an alkyl-magnesium halide and a halide of the metal in the presence of a non-reactive carrier liquid at a temperature below 50? 0., and finishing the reaction at a higher temperature. k

5. In a method of making a metal alkyl com )ound, the steps which consist in reacting etween an alkyl-magnesium-halide and a halide of the metal in the presence ofa nonreactive carrier liquid, at a temperature below 50 0., and finishing the reaction at a higher temperature, under pressure.

6. In a method of making a metal alkyl compound, the steps which consist in treating magnesium with an alkyl halide in a non-reactive solvent medium, adding to the resulting prodpct a halide of the metal at a temperature below 50 (1., and finishing the reaction by heatin at a temperature materially above 50 7. In a method of making a metal alkyl compound, the steps which consist in treating magnesium with an alkyl halide in a non-reactive solvent medium, adding to the resulting product a halide of the metal at a temperature below 50 (3., and finishing the reaction by heating at a temperature materially above 50 0., under pressure.

8. In a method of ma (ing a metal alkyl compound, the steps which consist in treating magnesium with an ethyl halide in a non-reactive solvent medium,adding to the resulting product a halide of the metal at a temperature below 50 C., and finishing the reaction by heatin at a temperature materially above 50 9. In a method of making a metal alkyl compound, the steps which consist in reacting between an alkyl-magnesium halide and a halide of the metal at a temperature below 50 C. in the presence of ether and an organic solvent having a higher boiling point than the ether, removing the ether, and then heating at a temperature materially higher than that of the initial reaction.

10. In a method of making a metal alkyl compound, the steps which consist in reacting between an alkyl-magnesium halide and a halide of the metal at a temperature below 50 C. in the presence of ether and a'solvent of higher boiling point than the ether, distilling oli the ether, and heating the initial product at a temperature materially above 50 C.

I 11. In a method of making a metal alkyl compound, the steps which consist in reacting between an alkyl-magnesium halide and a halide of the metal at a temperature below 50 C. in the presence of ether and an aromatic hydrocarbon solvent, distilling ofi the ether, and then heating the initial reaction product temperature materially above 50 C. 1 12. In a method of making a metal alkyl compound, the steps which consist in adding perature above 50 C.

14. In a method of making a lead alkyl compound, the steps which consist in reacting between an alkyl-magnesium halide and a halide of lead at a temperature not much exceeding room temperature, and heating the product so formed to a materially higher temperature.

15. In a method of making lead tetraethyl, the steps which consist in reacting between 'an ethyl-magnesiumhalide and. a halide of lead 'at a temperature not much exceeding room temperature, and heating the product so formed to a temperature above 50 C.

16. In a method of making lead tetraethyl, the steps which consist in reacting between an ethyl-magnesium halide and lead chloride at a temperature below 50 0., and heating the product so formed to a temperature materially above 50 C.

17. In a method of making lead tetraethyl, the steps which consist in reacting between an ethyl-Inagnesium-halide and a lead halide in the presence of a non-reactive carrier liquid, at a temperature not much in excess of room temperature, and finishing the reaction at a temperature materially higher.

18. In a method of making lead tetraethyl,

the steps which consist in reacting between an ethyl-magnesium-halide and a lead halide in the presence of a non-reactive carrier liquid, at a temperature below 50 (1., and finishing the reaction at a higher temperature.

.19. In a method of making a lead alkyl compound, the steps which consist in treating magnesium with an alkyl halide in a nonreactive solvent medium, adding to the resulting product a lead halide at a temperature below 50 C., and finishing the reaction by heaticng at a temperature materially above 50 20. In a method of making a lead alkyl compound, the steps which consist in treating magnesium with an ethyl halide in a non-reactive solvent medium, adding to the resulting product a lead halide at a temperature below 50 (1., and finishing the reaction by heating at a temperature materially above 50 C. p v

21. In a method of making lead tetraethyl, the steps which consist in reacting between an ethyl-magnesium halide and a lead halide at a temperature below 50 C. in the presence i of ether and a solvent having a higher boil- 50 C and finishing the reactionv at a higher 1 c with ethyl bromide,

ing point than ether, distilling ofi the ether, and then heating the initial reaction product at a temperature materially above 50 C.

22. In a method of making lead tetraethyl, the steps which consist in reacting between an ethyl-magnesium halide and a lead halide at a'temperature below 50 C. in the presence of ether and an aromatic hydrocarbon solvent, distilling oil? the ether, and then heating the initial reaction product at a temperature materially above 50 C.

23. In a method of making lead tetraethyl,

the steps which consist in reacting between an ethyl-magnesium halide and a lead halide in the presence of ether and toluene, distilling off the ether, and then heating the initial reaction product at a temperature materially above 50 C.

24. In a method of making lead tetraethyl, the steps which consist in adding an aromatic hydrocarbon solvent and lead chloride to an ethereal solution of an ethyl-magnesium halide, distilling ofi the ether, and then heating the initial reaction product at a temperature materially above 50 C.

25. In a method of making lead tetraethyl, the steps which consist in reacting between an ethyl-magnesium halide and lead chloride in the presence of ether and toluene at a temperature below 50 C., heating the initial product up to a temperature of approximately 90 to 95 (3., and refluxing the same at the latter temperature.

26. In a method of making a metal alkyl compound, the steps which magnesium with an alkyl bromide, then with an alkyl chloride in a non-reactive carrier liquid, treating the resulting compound with a halide of the metal at a temperature not consist in treating perature, and finishing the reaction at a temperature materially higher. I

30. In a method of making lead tetraethyl,

the steps which consist in treating magnesium I I 9QSigned by me this EDGAR o. Barrroiv;

much in excess of room temperature, and

reaction at a materially higher magnesium with an alkyl bromide, then with an alkyl chloride in a non-reactive carrier liquid, treating the resulting compound with a halide of the metal at a temperature below temperature, under pressure.

29. In a method of making lead tetraethyl, the steps which consist in treating magnesium then with ethyl chloride, in a non-reactive carrier liquid, treating the resulting compound with a lead halide at a temperature not much in excess of room tem- I 3d day of November, 

